The objectives of this project are: (1) to culture postimplantation embryos in order to aid the laboratory assessment of potential teratogens; (2) to define the mechanism of teratogenesis at the morphological, biochemical and molecular level using in vivo studies as well as cultured embryos exposed to teratogens of interest; (3) to determine the role that various hormones and growth factors play in early postimplantation embryonic development.